Castro, Robert P. (Sunnyvale, CA)
Baker, Richard W. (Palo Alto, CA)
Wijmans, Johannes G. (Menlo Park, CA)

07/450278

09/17/1991

12/13/1989

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Membrane Technology & Research, Inc. (Menlo Park, CA)

95/55

96/13, 96/12

B01D69/12; B01D69/00; B01D53/22

55/16, 55/68, 55/158

4230463	Multicomponent membranes for gas separations	October, 1980	Henis et al.	55/68
4243701	Preparation of gas separation membranes	January, 1981	Riley et al.	427/244
4277344	Interfacially synthesized reverse osmosis membrane	July, 1981	Cadotte	210/654
4444662	Microporous laminate	April, 1984	Conover	55/158
4470831	Permselective membrane	September, 1984	Hirose	55/158
4484935	Permeation modified membrane	November, 1984	Zampini	55/158
4493714	Ultrathin film, process for production thereof, and use thereof for concentrating a specified gas in a gaseous mixture	January, 1985	Ueda et al.	55/16
4528004	Aromatic polyimide composite separating membrane	July, 1985	Makino et al.	55/158
4553983	Process for recovering organic vapors from air	November, 1985	Baker	55/16
4559139	High performance semipermeable composite membrane and process for producing the same	December, 1985	Uemura et al.	210/490
4581043	Composite dense membrane	April, 1986	van der Scheer	55/16
4594079	Gas separating member and method for manufacture thereof	June, 1986	Yamamoto et al.	55/158
4602922	Method of making membranes for gas separation and the composite membranes	July, 1986	Cabasso et al.	55/158
4631075	Composite membrane for gas separation	December, 1986	Yamabe et al.	55/158
4666668	Gas-permeable membrane, and blood oxygenator based on gas-permeable membrane	May, 1987	Lidorenko et al.	55/158
4713292	Multilayer composite hollow fibers and method of making same	December, 1987	Takemura et al.	55/158
4772394	Chlorine-resistant semipermeable membranes	September, 1988	Swedo et al.	55/158
4781733	Semipermeable thin-film membranes comprising siloxane, alkoxysilyl and aryloxysilyl oligomers and copolymers	November, 1988	Babcock et al.	55/16
4857078	Process for separating higher hydrocarbons from natural or produced gas streams	August, 1989	Watler	55/158
4857080	Ultrathin composite metal membranes	August, 1989	Baker et al.	55/158
4871378	Ultrathin ethylcellulose/poly(4-methylpentene-1) permselective membranes	October, 1989	Pinnau	55/16

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JP59049805	March, 1984		55/158	PERMSELECTIVE MEMBRANE FOR SEPARATION OF GAS
JP61291018	December, 1986		55/158	GAS PERMEABLE LAMINATED BODY
JP62106810	May, 1987		55/158	SEPARATING MEMBRANE FOR OSMOSIS VAPORIZATION
JP63296823	December, 1988		55/158	OXYGEN-ENRICHING MEMBRANE AND PRODUCTION THEREOF
JP63305918	December, 1988		55/158	GAS SEPARATION MEMBRANE

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Spitzer, Robert

Farrant J.

We claim:

1. A separation process, comprising the steps of:

(a) providing a separation membrane having a feed side and a permeate side, said membrane comprising:

a microporous substrate layer;

a sealing layer coating said microporous substrate layer;

an interfacially polymerized permselective layer formed on said sealing layer;

(b) contacting said feed side with a feed fluid mixture comprising component A and component B;

(c) withdrawing from said permeate side a gas mixture enriched in component A compared with said feed fluid mixture.

2. The process of claim 1, wherein said component A is hydrogen.

3. The process of claim 1, wherein said component A is hydrogen and said component B is carbon dioxide.

4. The process of claim 1, wherein said membrane has a selectivity for component A over component B of at least 10.

5. The process of claim 1, wherein said sealing layer comprises a polymer that takes no part in a reaction used to form said permselective layer.

6. The process of claim 1, wherein said permselective layer is selectively permeable to hydrogen over carbon dioxide.

7. A membrane suitable for use in gas separation or pervaporation, comprising:

a microporous substrate layer;

a sealing layer coating said microporous substrate layer;

an interfacially polymerized permselective layer formed on said sealing layer.

8. The membrane of claim 7, wherein said permselective layer is produced by reacting a first reagent and a second reagent, both reagents having two or more functional groups.

9. The membrane of claim 8, wherein said first reagent has two functional groups and said second reagent has three functional groups.

10. The membrane of claim 8, wherein said first reagent is a diamine.

11. The membrane of claim 10, wherein said diamine is 1,6-hexane diamine.

12. The membrane of claim 8, wherein said second reagent is a trifunctional acyl halide.

13. The membrane of claim 12, wherein said trifunctional acyl halide is 1,3,5-benzene tricarbonyl trichloride.

14. The membrane of claim 7, having a sealing layer comprising a rubbery polymer.

15. The membrane of claim 7, having a sealing layer comprising silicone rubber.

16. The membrane of claim 7, characterized in that the membrane exhibits a selectivity for a more permeable gas over a less permeable gas of at least 10.

17. The membrane of claim 16, wherein said more permeable gas is hydrogen.

18. The membrane of claim 17, wherein said less permeable gas is carbon dioxide.

19. The membrane of claim 7, wherein said sealing layer comprises a polymer that takes no part in a reaction used to form said permselective layer.

20. The membrane of claim 7, wherein said permselective layer is selectively permeable to hydrogen over carbon dioxide.

21. A process for preparing a separation membrane, comprising: providing a microporous substrate;

coating said substrate with a sealing layer, to form a composite support membrane;

contacting said composite support membrane with a first solution containing a first reagent for a first contact period; and

contacting said composite support membrane with a second solution containing a second reagent for a second contact period.

22. The process of claim 21, wherein said first solution comprises an organic solvent.

23. The process of claim 22, wherein said organic solvent comprises hexane.

24. The process of claim 21, wherein said first solution comprises water.

25. The process of claim 21, wherein said first reagent has at least two functional groups.

26. The process of claim 21, wherein said first reagent is a diamine.

27. The process of claim 21, wherein said first reagent is 1,6-hexane diamine.

28. The process of claim 21, wherein said first reagent is trifunctional acyl halide.

29. The process of claim 21, wherein said trifunctional acyl halide is 1,3,5-benzene tricarbonyl trichloride.

30. The process of claim 21, wherein said first contact time is up to 30 minutes.

31. The process of claim 21, wherein said second contact time is up to 10 minutes.

EXAMPLES

Examples 1-10

A set of experiments was performed to prepare interfacially polymerized permselective membranes from a selection of reagents. The composite support membrane was the same in each case. Interfacially polymerized layers were formed on the support using the sets of reagents shown in Table 1.

TABLE 1

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Reagents used to make Interfacially Polymerized Membranes Water-soluble reagent Organic-soluble reagent

______________________________________

##STR1## ##STR2## ##STR3## ##STR4## ##STR5## ##STR6## ##STR7## ##STR8## ##STR9## ##STR10##

______________________________________

Example 1. Preparation of composite support membrane.

Composite support membranes were prepared by first casting a microporous membrane on a polyester web, then coating the microporous membrane with a thin sealing layer. The casting solution, consisting of 17.5 wt % UDEL® P3500 (Amoco Co, Marietta, OH) in 82.5 wt % dimethylformamide, was doctored onto a moving non-woven, polyester web. The casting speed was 3.5 m/min and the knife gap was 178 μm. The belt passed into a water bath, which precipitated the polymer to form the microporous membrane. The belt was then collected on a take-up roll, the membrane was washed overnight to remove any remaining solvent and dried to form the microporous membrane. The dip-coating operation was then performed as follows. The polysulfone membrane was fed from a feed roll through a coating station containing 1.8 wt % polydimethylsiloxane (Wacker Silicones Co., Adrian, MI), in 98.2 wt % 2,2,4-trimethylpentene. The coated membrane passed through a drying oven, and was wound up on a product roll. This operation coated the traveling microporous membrane with a liquid layer, 50 to 100 μm thick. After evaporation of the solvent, a polymer film, 0.5 to 2 μm thick, was left on the membrane. Similar coating operations were carried out using polymethylpentene, TPX® MX 002 (Mitsui Co., New York, NY) and a polyamide copolymer, Pebax® 4011 (Atochem Inc, Glen Rock, NJ) as the sealing layer.

The finished thickness of the sealing layer of the composite support membranes was obtained by comparing its nitrogen flux with values obtained from isotropic films of known thickness. The sealing layer was checked for integrity by measuring the ratio of the oxygen and nitrogen permeabilities. Only those supports where the measured selectivity was close to the intrinsic selectivity of the coating polymer were used in the interfacial polymerization experiments.

The composite support membranes that passed the integrity test were tested for hydrogen and carbon dioxide permeability using a permeation test cell. The permeate gas flow rate was measured with bubble flowmeters, then converted into a normalized permeation rate at a standard pressure difference (1 cmHg) and a standard membrane area (1 cm ² ). The pressure on the feed side of the cell was 200 psig. The permeate side was at atmospheric pressure. The test cell had a membrane area of 36.8 cm ² . The results are summarized in Table 2.

TABLE 2

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Normalized Permeation Rates and Hydrogen/Carbon Dioxide of Composite Support Membranes with Various Sealing Layers Composite Normalized Permeation Rate Support (cm 3 (STP)/cm 2  s  cmHg) Selectivity Membrane H 2 CO 2 H 2 /CO 2

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Polysulfone 9.0 × 10 -2 3.3 × 10 -2 2.7 (PSF) alone PSF/silicone 6.1 × 10 -4 2.3 × 10 -3 0.26 rubber PSF/poly- 5.6 × 10 -5 5.0 × 10 -5 1.1 methylpentene PSF/poly- 1.7 × 10 -5 4.5 × 10 -5 0.38 amide copolymer

______________________________________

Example 2

An interfacially polymerized permselective layer was formed on the composite support membrane of Example 1 that had a silicone rubber sealing layer. The preparation technique was as follows. The interfacially polymerized layer was made by submerging the composite support membrane in a hexane solution containing 0.5 wt % toluene-2,4-diisocyanate.

After thirty minutes, the composite support membrane was removed from the hexane bath and held vertically for one minute to drain excess solution. The composite support membrane was then submerged in an aqueous polyethyleneimine (PEI) solution, containing 1.0 wt % PEI (MW 70,000) in 99.0 wt % distilled water. After five minutes, the membrane was removed from the aqueous bath and air-dried at room temperature.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 3

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous PEI solution containing 1.0 wt % PEI (MW 10,000) and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 4

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous piperazine solution containing 1.0 wt % piperazine and 1.0 wt % potassium hydroxide in 98.0 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 5

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous 1,3-propane diamine solution containing 1.0 wt % dimamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 6

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous 1,6-hexane diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 7

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous 1,9-nonane diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 8

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous 1,3-phenylene diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

Example 9

The procedure of Example 2 was repeated using a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride and an aqueous 1,4-phenylene diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 3.

TABLE 3

______________________________________

Normalized Permeation Rates and Hydrogen/Carbon Dioxide Selectivity for Various Interfacial Composite Membranes Normalized Permeation Rate (cm 3 (STP)/ Ex- cm 2  s  cmHg) Selectivity ample Reagent H 2 CO 2 H 2 /CO 2

______________________________________

2. PEI/TDI 3.6 × 10 -6 1.2 × 10 -5 0.30 3. PEI/BTC 1.1 × 10 -6 5.0 × 10 -6 0.22 4. Piperazine/BTC 2.5 × 10 -6 1.4 × 10 -6 2.1 5. 1,3-propane- 2.9 × 10 -6 3.2 × 10 -6 0.91 diamine/BTC 6. 1,6-hexane- 4.4 × 10 -6 3.2 × 10 -7 14 diamine/BTC 7. 1,9-Nonane- 7.8 × 10 -6 1.1 × 10 -6 7.1 diamine/BTC 8. 1,3-Phenylene- 2.9 × 10 -6 1.1 × 10 -6 2.6 diamine/BTC 9. 1,4-Phenylene- 1.8 × 10 -5 6.7 × 10 -6 2.7 diamine/BTC

______________________________________

PEI: polyethyleneimine TDI: toluene diisocyanate BTC: 1,3,5benzene tricarbonyl trichloride

Examples 2 and 3 were prepared from a polyamine and a diisocyanate, and a polyamine and a trifunctional agent, respectively. As can be seen, the membranes prepared using polyamines, preferred for the preparation of reverse osmosis membranes, did not form adequate gas separation membranes. The selectivities obtained are essentially those of the silicone rubber sealing layer.

Examples 10-15

A series of membranes was prepared using the same reagents and general procedure as in Example 6. The same time of contact between the composite support membrane and hexane phase, and between the hexane loaded support and the aqueous phase was used in each case.

Example 10

An interfacially polymerized membrane was prepared as follows. A composite support membrane was a silicone rubber sealing layer was prepared and tested for integrity as in Example 1. The interfacially polymerized layer was made by submerging the composite support membrane in a hexane solution containing 1 wt % 1,3,5-benzene tricarbonyl trichloride.

After one minute, the composite support membrane was removed from the hexane bath and held vertically for one minute to drain excess solution. The composite support membrane was then submerged in an aqueous 1,6-hexane diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water. After one minute, the membrane was removed from the aqueous bath and air-dried at room temperature.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

Example 11

The procedure as in Example 10 was repeated, using immersion and contact times of five minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

Example 12

The procedure as in Example 10 was repeated, using immersion and contact times of 10 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

Example 13

The procedure as in Example 10 was repeated, using immersion and contact times of 15 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

Example 14

The procedure as in Example 10 was repeated, using immersion and contact times of 30 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

Example 15

The procedure as in Example 10 was repeated, using immersion and contact times of 60 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 4.

TABLE 4

______________________________________

Normalized Permeation Rate and Selectivity Data for 1,3,5- Benzenetricarbonyl Trichloride/1,6-Hexanediamine Interfacial Composite Membranes Using Various Solution Contact Times. Solution Ex- Contact Normalized Permeation Rate Select- am- Time* (cm 3 (STP)/cm 2  s  cmHg) ivity ple (min) N 2 H 2 CO 2 H 2 /CO 2

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10. 1 3.6 × 10 -7 1.7 × 10 -6 9.1 × 10 -7 1.9 11. 5 ** 4.2 × 10 -6 ** -- 12. 10 3.0 × 10 -7 2.6 × 10 -6 2.7 × 10 -7 9.6 13. 15 ** 5.1 × 10 -6 3.1 × 10 -7 16 14. 30 ** 6.0 × 10 -6 4.5 × 10 -7 13 15. 60 2.9 × 10 -7 2.8 × 10 -6 1.9 × 10 -7 14

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*Time of contact between composite support membrane and hexane phase and between hexane phase and aqueous phase. **Permeation rate too slow to measure.

Examples 16-19

A series of membranes was prepared using the same reagents and general procedure as in Example 10-15. In this case, the same immersion time was used for all the experiments, but the contact time between the reagents was varied.

Example 16

An interfacially polymerized membrane was prepared as follows. A composite support membrane with a silicone rubber sealing layer was prepared and tested for integrity as in Example 1. The interfacially polymerized layer was made by submerging the composite support membrane in a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride.

After 30 minutes, the composite support membrane was removed from the hexane bath and held vertically for one minute to drain excess solution. The composite support membrane was then submerged in an aqueous 1,6-hexane diamine solution containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water. After one minute, the membrane was removed from the aqueous bath and air-dried at room temperature.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 5.

Example 17

The procedure as in Example 16 was repeated, using an immersion time of 30 minutes and a contact time between the reagents of 5 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 5.

Example 18

The procedure as in Example 16 was repeated, using an immersion time of 30 minutes and a contact time between the reagents of 10 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 5.

Example 19

The procedure as in Example 16 was repeated, using an immersion time of 30 minutes and a contact time between the reagents of 30 minutes.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 5.

TABLE 5

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Normalized Permeation Rates and Hydrogen/Carbon Dioxide Selectivities of 1,3,5-Benzenetricarbonyl Trichloride/1,6-Hex- anediamine Interfacial Composite Membranes Prepared by Vary- ing the Reagent Contact Time. Example Number Normalized Permeation Rate and Contact (cm 3 (STP)/cm 2  s  cmHg) Selectivity Time (min) N 2 H 2 CO 2 H 2 /CO 2

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16. 1 -- 5.6 × 10 -6 4.0 × 10 -7 14 17. 5 9.2 × 10 -8 4.4 × 10 -6 3.2 × 10 -7 14 18. 10 1.7 × 10 -7 6.4 × 10 -6 5.9 × 10 -7 11 19. 30 1.1 × 10 -7 4.6 × 10 -6 5.4 × 10 -7 8.5

______________________________________

The data in Table 5 show that a contact time of only one minute was sufficient in this case for the interfacial polymerization reaction to occur.

Comparing the sets of examples 10-15 and 16-19, it appears that the increase in hydrogen/carbon dioxide selectivity with increasing contact times shown in Table 4 is the result of increased penetration of the BTC into the silicone rubber sealing layer.

The data in Table 5 show that the permeation rates of the membrane do not decrease with increasing contact time between the hexane-soaked composite support membrane and the aqueous 1,6-hexane diamine solution. This suggests that after the initial interfacial polymerized layer is formed, the reaction essentially ceases due to slow amine diffusion through the interfacial layer.

Examples 20-27

Interfacially polymerized composite membranes were prepared as in Example 17. The membranes were tested using the procedure described in Example 1 with the following pure gases: helium, hydrogen, oxygen, nitrogen, methane, carbon dioxide, ethane, propane, and butane. The results are summarized in Table 6.

TABLE 6

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Normalized Permeation Rates and Selectivities for a BTC/1,6- Hexanediamine Interfacial Composite Membrane Normalized Flux Selectivity Example Gas cm 3 (STP)/cm 2  s  cmHg Hydrogen/gas

______________________________________

20 He 2.9 × 10 -6 0.83 21 H 2 2.5 × 10 -6 1.0 22 O 2 6.7 × 10 -8 37 23 N 2 2.0 × 10 -8 125 24 CH 4 4.3 × 10 -8 58.8 25 CO 2 1.8 × 10 -7 13.8 26 C 2 H 6 8.3 × 10 -8 30.3 27 C 3 H 8 2.2 × 10 -7 11.3

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The performance of the interfacial composite membrane is typical of the behavior of glassy polymers, in that small molecules permeate preferentially compared with larger molecules. The hydrogen/carbon dioxide selectivity of the interfacial composite membrane is exceptionally high.

Examples 28-31

A series of experiments was carried out using the same general preparation technique and immersion and contact times as in Example 17, but with various types of polymers for the composite support membrane sealing layer.

Example 28

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1. The membrane was not coated with a sealing layer. An interfacially polymerized layer was formed on the uncoated support as follows. The support membrane was submerged in a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride.

After 30 minutes, the composite support membrane was removed from the hexane bath and held vertically for one minute to drain excess solution. The composite support membrane was then submerged in an aqueous 1,6-hexane diamine solution containing 1.0 wt % diamine and 1.0 wt % potassum hydroxide in 98 wt % distilled water. After five minutes, the membrane was removed from the aqueous bath and air-dried at room temperature.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 7.

Example 29

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1, with a silicone rubber sealing layer. An interfacially polymerized layer was formed on the composite support membrane using the same procedure as in Example 28.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 7.

Example 30

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1, with a polymethylpentene sealing layer prepared from a 2.0 wt % solution of polymethylpentene (TPX® MX 002, Mitsui Co, New York, N.Y.) in 98 wt % cyclohexane. An interfacially polymerized layer was formed on the composite support membrane using the same procedure as in Example 28.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 7.

Example 31

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1, with a sealing layer prepared from a 1.0 wt % polyamide copolymer (Pebax® 4011, Atochem, Inc., Glen Rock, N.J.) in 99.0 wt % butanol solution. An interfacially polymerized layer was formed on the composite support membrane using the same procedure as in Example 28.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 7.

TABLE 7

______________________________________

Normalized Permeation Rates and Selectivities of 1,3,5-Benzene- tricarbonyl Trichloride 1,6-Hexanediamine Interfacial Polymer- ized Layers Formed on Different Composite Support Membranes. Normalized Permeation Composite Rate (cm 3 (STP)/ Support cm 2  s  cmHg) Selectivity Example Membrane H 2 CO 2 H 2 /CO 2

______________________________________

28. Polysulfone 2.2 × 10 -5 4.5 × 10 -6 4.9 (PSF)alone 29. PSF/silicone 5.1 × 10 -6 3.1 × 10 -7 16 rubber 30. PSF/poly- 1.8 × 10 -6 1.5 × 10 -7 12 methylpentene 31. PSF/polyamide 4.8 × 10 -6 3.2 × 10 -6 1.5 copolymer

______________________________________

Comparison of the results from examples 28-31 shows that an interfacially polymerized membrane prepared on a support without a sealing layer did not yield a gas separation membrane with good properties. The polyamide copolymer sealing layer also resulted in a membrane with poor hydrogen/carbon dioxide selectivity. However, in this case, the polyamide copolymer alone has a selectivity for carbon dioxide over hydrogen of about 15. That the finished interfacial composite is selective for hydrogen over carbon dioxide at all shows the powerful influence of the interfacially polymerized layer.

Examples 32-33

Two experiments was carried out following the same general preparation techniques and procedures as Examples 28-31. In this case, however, the support was immersed in the aqueous solution, then contacted with the organic solution.

Example 32

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1. The membrane was not coated with a sealing layer.

An interfacially polymerized layer was formed on the support as follows. The support membrane was submerged in an aqueous solution of 1,6-hexane diamine containing 1.0 wt % diamine and 1.0 wt % potassium hydroxide in 98 wt % distilled water.

After 30 minutes, the composite support membrane was removed from the water bath and held vertically for one minute to drain excess solution. The composite support membrane was then submerged in a hexane solution containing 1.0 wt % 1,3,5-benzene tricarbonyl trichloride. After five minutes, the membrane was removed from the hexane bath and air-dried at room temperature.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 8.

Example 33

An asymmetric microporous support membrane was cast using the same recipe and procedure as in Example 1, with a polyamide copolymer sealing layer as in Example 31. An interfacially polymerized layer was formed on the composite support membrane using the same procedure as in Example 32.

The resulting membrane was tested in a permeation cell using the same procedure as was used to evaluate the composite support membranes described in Example 1. The results are summarized in Table 8.

TABLE 8

______________________________________

Normalized Permeation Rates and Selectivities of 1,3,5-Benzene- tricarbonyl Trichloride 1,6-Hexanediamine Interfacial Polymer- ized Layers Formed by Immersion in Aqueous Phase followed by contact with Organic Phase Normalized Permeation Composite Rate (cm 3 (STP)/ Support cm 2  s  cmHg) Selectivity Example Membrane H 2 CO 2 H 2 /CO 2

______________________________________

32. Polysulfone 3.4 × 10 -3 1.1 × 10 -3 3.1 (PSF)alone 33. PSF/polyamide 2.0 × 10 -5 6.2 × 10 -6 3.2 copolymer

______________________________________

Example 34

A test was performed to determine whether the interfacially polymerized layer extends into the matrix of the sealing layer. An interfacially polymerized membrane was prepared as in Example 17, with a silicone rubber sealing layer and an interfacial layer formed by the reaction of 1,3,5-benzenetricarbonyl trichloride with 1,6-hexane diamine. The resulting membrane was soaked in water for two hours, then dried and tested. The hydrogen permeation rate increased by a factor of three, whereas the other gas permeation rates increased by more than a factor of three. The membrane was then again soaked in water for two hours. This time, before the membrane was allowed to dry, the membrane surface was rubbed in an attempt to remove the interfacial polymerized layer. Upon retesting, the membrane properties were close to those of the silicone rubber/polysulfone composite support membrane in both permeation rates and selectivities. The interfacial layer had been removed, indicating that the polymerization reaction does not proceed substantially into the silicone rubber matrix.